The Champions League is better than it sounds. When the season gets serious it is not any sort of league. Just as well. The group phase is a fine reminder of how tedious an elite can be when seeding stops its members from facing one another. There was just an illusion of spontaneity when Liverpool and Juventus, currently nondescript even in domestic competition, were eliminated. Only now can the Champions League take a grip on the imagination.

Group winners, admittedly, are kept apart a little longer and have home advantage for the return match in the last 16 ties that start tomorrow, but enough unpredictability survives. Whether out of altruism or an appreciation that revenue depends on public interest, Uefa has kept monotony at bay. In 2003, for instance, the organisers ended the insufferable spell in which there were two group phases.

It would take extraordinary economic shifts before Steaua Bucharest or Red Star Belgrade could envisage regaining the European Cup, but there is still diversity. No winner, after all, has retained the prize since Milan 20 years ago. The silverware still stacks up air miles and has made its way round trophy rooms in four countries over the past six years.

That spell opened with Porto beating the even more unlikely finalists Monaco in 2004. Success is personalised whenever José Mourinho is involved and he had already drawn attention to himself by taking the Uefa Cup the season before, but the Champions League is elusive enough to ensure that it will not be mistaken for his personal property.

Despite enhanced means, he never went beyond the last four at Chelsea and was eliminated with Inter when obliged to take on Manchester United at the start of the knockout phase a year ago. The bookmakers foresee another anti-climax for Mourinho in the tie with the Stamford Bridge club that begins next week. Still, there is a chance of the tournament upsetting the odds, even if the shock does not come in London.

Maybe, for instance, a Bayern Munich under the command of Louis van Gaal might develop some conviction. Thanks to commercial income this is an affluent club that ought to achieve more in the Champions League than they have of late. The immediate prospect for Bayern is enticing since Fiorentina lie 11th in Serie A and seemed to be feeling the strain even before Adrian Mutu was reported last month to have tested positive for a banned appetite suppressant.

Where Germany is concerned, even Stuttgart have grounds for tentative hope. Though they are pitted against Barcelona, the magnificent holders are hindered a little. An under-strength line-up lost at Atlético Madrid on Sunday and Pep Guardiola will still lack Dani Alves, Xavi and most likely Yaya Touré next week. That does not seem sufficient to bring down a wonderful team, but the stresses undergone with club and, where Spaniards are concerned, country have been intense for a while now because honours are pursued on so many fronts. To a lesser degree, Real Madrid will be on edge because a great deal is demanded of men who cost so much in wages and transfer fees.

A rather less glamorous Chelsea feel some of those pressures, if not to the same extent. Manchester United will be glad of any lack of attention as they busy themselves with an unexpected revival. They have lost Cristiano Ronaldo, they have not spent heavily, they have watched their one costly signing from the past two summers, Dimitar Berbatov, marginalise himself, their defence was thrown together out of whatever remained while Rio Ferdinand and Nemanja Vidic were injured and the reliance on old-timers such as the injured Ryan Giggs or, to a degree, Paul Scholes, is not easing.

Despite it all, they looked exactly as they have so often in the past when, down to 10 men for an hour in the draw at Villa Park last week, they dominated and would have merited a win. Such an upsurge is in United's nature, but it is inexplicable in any specific sense. That factor might make rivals all the more apprehensive. A third consecutive appearance in the Champions League final will not seem beyond hope for Sir Alex Ferguson, even if it should be.

All the same, the burdens on the domestic front may eventually take their toll on Chelsea and United. Perhaps Arsenal, whose tie with Porto begins on Wednesday can give more of themselves in Europe since their Premier League fortunes are no longer in their own hands. The flaws are evident, but they were, too, in 2006 when Arsenal, with a line-up past its peak, still led Barcelona before their eventual defeat in the final despite having Jens Lehmann sent off in the 18th minute.

The Barcelona squad has the talent to retain the Champions League if exhaustion is kept at bay, but nothing can be taken for granted. For all its corporate appearance, this is a tournament that retains an element of surprise.